Board chair Larry Schallock declined to provide a reason for the decision.

“Larry Anderson is on paid administrative leave in relation to a personnel matter,” Schallock said. “Other than that, I have no comment.”

Anderson did not respond Thursday afternoon to a request for comment left on his personal cellphone. Schallock said Casey Fatch, the hospital’s chief operating officer, is serving as interim CEO.

Anderson joined Tri-City as interim CEO in early 2009, after the hospital board sidelined most of its executive team during a closed-session meeting. Most of the executives were eventually fired, though the investigation that led to that action was never made public.

Anderson has worked over the last four years to turn Tri-City’s finances around. When he took over in early 2009, Tri-City was more than $5 million in the red and had just lost a major piece of its referral base when a large doctors’ group started referring patients south to Scripps Memorial Hospital Encinitas. Anderson launched initiatives that produced profits in the 2011 and 2012 budget years. But the turnaround didn’t last.

As of June, the hospital was running an $11 million loss for the budget year that ended in July. A final accounting for the year was not available Thursday.

Though finances have sometimes been a challenge, the hospital has posted decent quality scores with Anderson at the helm. For example, the Leapfrog Group, a nonprofit that rates hospitals on a spectrum of safety measures, graded the facility a solid B.

But the CEO has come under fire for his management style.

In October 2012, for example, Steven Daniel Stein, the hospital’s former vice president of legal affairs, filed a multimillion-dollar federal lawsuit against Tri-City alleging that Anderson was abusive to employees, berating some for taking time off work for medical reasons. In June a federal judge denied Tri-City’s motion to dismiss a key claim of Stein’s suit — that he was fired in fear that he would blow the whistle to authorities regarding workplace discrimination.

It was not clear Thursday whether the lawsuit or Tri-City’s recent losses had anything to do with the board’s decision.

Schallock declined to say how many board members voted to put Anderson on leave, how long that hiatus might last or whether there is an investigation. The hospital board met in closed session Wednesday evening with only a discussion of “potential litigation” on the agenda.

After leaving closed session, the board did not report its decision to the public in open session.

Open meetings law requires public bodies like the Tri-City board, which is composed of seven elected directors from Vista, Oceanside and Carlsbad, to report any action taken behind closed doors. However, Greg Moser, Tri-City’s attorney, said the law does not require the board to report its vote to the public until after an employee has exhausted all possible “administrative remedies.”

Those remedies are spelled out in Anderson’s 16-page contract, which runs through Aug. 16, 2014. Anderson is allowed to terminate the agreement if the board makes “any material diminution or modification” of his duties as CEO.